Fundamentals, water, acids, bases and buffers Flashcards
Enzyme deficiency in alkaptonuria
Homogentisate oxidase
Enzyme deficiency in homocystinuria
Cystathionine synthase
Enzyme deficiency in MSUD
Branched-chain alpha-ketoacid dehydrogenase
Enzyme deficiency in PKU
Phenylalanine hydroxylase
Hydroxylation
Introduces an -OH group
Decarboxylation
removes a carboxyl group and release CO2
IN oxidation reactions electrons are ____
IN reduction reactions electrons are ____
Lost
Gained
___% of our body wieght is water
50%
Unique properties of water
Great nucleophile
Great buffer
Hydrogen bonds
Great solvent
pH =
- log [H+]
Hormones that monitor blood volume and osmolality
ADH and aldosterone
Buffers consist of:
Undissosciated acid and its conjugate base
A buffer has its greatest buffering cpacity at:
or near its pKa (+/- 1)
pKa =
- log Ka
Two factors that determine the effectiveness of a buffer
its pKa relative to the pH of a solution
and
its concentration
Norma pH range for blood
7.35 - 7.45
Blood pH is maintained by:
H2CO3/HCO3- buffer system
Ka is:
acid dissociation constant, larger Ka, stronger acid
pKa is:
- log Ka
smaller pKa, stronger acid
Henderson-Hasselbalch equation:
pH = pKa + log [A-]/[HA]
Normal metabolism generates:
CO2, lactic acids and ketones, and inorganic acids
How does the body void of acid?
Expiration of CO2
Excretion of ammonium (NH4+)
Respiratory acidosis caused by:
Hypoventilation > leads to an increase in CO2 > increase H+ > decreased pH
Metabolic acidosis caused by:
Addition of a strong acid and loss of HCO3- (via diarrhea and/or abnormal kidney function)
Buffer system equation (dont forget enzyme):
CO2 + H2O H2CO3 HCO3- + H+
Via carbonic anhydrase
Respiratory alkalosis is caused by:
Hyperventillation > leads to decrease in CO2 > leads to loss of H+ > increased pH
Metabolic alkalosis caused by:
Addition of a strong base and loss of acid (via vomiting)
Gibbs free energy:
∆G = ∆H -T∆S
-∆H vs +∆H
-∆H is favorable and leads to a lower energy state, heat flow out of the system
+∆H is unfavorable and leads to higher energy state, heat flow into a system
-∆S vs +∆S
-∆S more favorable as ti leads to increase in entropy
+∆S less favorable as it leads to a decrease in entropy
What is Keq
Equilibrium cosntant
Temperature dependent
Keq =
[X]^x[Y]^y / [A]^a[B]^b
for reaction:
aA +bB xX + yY
Standard state conditions
298K, 1M, 1 atm, pH 7
∆G°
vs
∆G°’
Gibbs free energy under standard conditions
Same, but used for biochemistry purposes
∆G° > 0 (+)
Endergonic
non spontaneous
favors reactants
∆G° < 0 (-)
Exergonic
spontaneous
favors products
Le Chatliers Principle
Systems at equilibrium will respond to applied stress with a shift that counteracts applied stress
+∆H
vs
-∆H
Endothermimc
Exothermic
Chemical reaction that is crucial to creating energy currency ATP
Phosphoryl group transfer
Favorability of ATP -> ADP + Pi
Very favorable
∆G «_space;0
ATP hydrolysis is useful in coupling reactions
Cystine
When 2 Cysteine’s come together by a disulfide bond
Charge on α-amino group
pronated (+) at a pH 7
Charge on α-carboxyl group
dissociated (-) at pH 7
Charge on basic AA’s
Arginine, lysine, histidine are positive at pH 7
Charge on acidic AA’s
Aspartic acid and glutamic acid are negative at pH 7
Isoelectric point
Point at which overall charge on AA is 0
If the pH is below pKa:
It will be pronated
If the pH is above pKa:
It will be deprotonated
pK1
α-carboxyl group (pKa ~2)
pK2
α-amino group (pKa ~9)
First line of defense against pH shift
Bicarbonate buffer
Phosphate buffer
Protein buffer (ie hemoglobin)
Second line if defense against pH shift
Respiratory mechanism (excretion of CO2) Renal mechanism (excretion of H+)
Why does a patient with severe anemia have a decreased capacity to use the bicarbonate buffer system?
Decreased amount of carbonic anhydrase in red blood cells
Enzyme deficiency in homocystinuria:
Cystathione synthase
Enzyme deficiency in alkaptonuria:
Homogentisate oxidase
A class of chemical reactions that are of great importance in the formation of energy currency ATP
Phosphoryl group transfer
